Re: New Math Coprocessor - who has a need for it???

[dempson@swell.actrix.gen.nz (David Empson)]

In article <CA8u44.5II@wave.scar.utoronto.ca> 90taobri@wave.scar.utoronto.ca (Brian Tao) writes:
> 
>     Why can't math copros and DSP's speed up integer math as well? 
> Sure, FP math is slower, but int math is used in more places.

A 68881 or 68882 doesn't support integer maths (other than converting
integer types into floating point types, and using 64-bit integers).

A DSP would not accelerate addition or subtraction (there would be too
much overhead getting the data in and out), but could help with
multiplication and division.

The 65816 has no instructions to perform multiply and divide
operations, so it has to synthesize them using addition/subtraction and
shifting in a loop.

A DSP supports multiplication and division directly, so you could
patch out the various multiply and divide routines in the IntMath
toolset to use a DSP instead.  Provided the data exchange didn't take
too long, this should improve the speed of some programs.

I don't know if QuickDraw uses the IntMath toolset, or includes its
own code for doing integer multiplication and division.

It wouldn't help with programs that incorporate their own code to do
multiplication and division (I think this includes and ORCA/C,
ORCA/Pascal, and also any ORCA/M programs that use the macros and
library supplied with the assembler).
-- 
David Empson                                                               
dempson@swell.actrix.gen.nz                                                
Snail mail: P.O. Box 27-103, Wellington, New Zealand